Efficient syntheses of dihydroquinazolines

NADIA GRUBER; JIMENA E. DÍAZ; LILIANA R. ORELLI

Marsella

Simposio; 18th European Symposium on Organic Chemistry; 2013

Cyclic amidines are heterocyclic cores of wide pharmacological interest. In particular, some dihydroquinazolines have shown antibacterial and antiplatelet activity. The reported synthetic pathways for the dihydroquinazoline nucleus generally involve drastic reaction conditions, require selective N-monoprotection steps and/or lead to poor yields. In this context, we present here efficient methods for the synthesis of novel 1,4- and 3,4-dihydroquinazoline derivatives with different N-substitution patterns. Scheme 1: Proposed syntheses of selectively N-substituted dihydroquinazolines The synthetic routes share 2-aminobenzylamine as the common precursor. The cyclodehydration reactions leading to the heterocycles were promoted by PPE (ethyl polyphosphate), a mild dehydrating agent of the Lewis acid type, and accelerated by microwaves.